1. Field of the Invention
This invention relates to submarine cable laying and, in particular, to apparatus for measuring cable tension and telemetering tension and range measurements by wireless means during such operations.
2. Description of the Prior Art
The art of submarine cable laying from surface ships is an ancient one. A recurring problem which has had many partial solutions is that of monitoring cable tension while deploying the cable. Typically, tension in the cable being deployed is measured by passing the cable over a suitably configured load cell positioned just ahead of the outboard launching sheave. It has not been the practice to attempt tension measurements in the cable span between the sea surface and ocean bottom. This arrangement has been reasonably satisfactory as long as cables were ruggedized by external armor. Recently the development of lightweight cables whose strength member is located at the cable core has made possible the streaming of longer continuous cable lengths without reloading. Significant weight reduction has also been attained through the use of glass fibers, which permit expanded signaling bandwidths, but at the expense of greater fragility. Consequently, the monitoring of cable tension during launching operations becomes more critical than heretofore. Greater precision of measurement also becomes necessary.
It is an object of this invention to provide means for monitoring of tension at selected locations along the catenary of a submarine cable during deployment from a surface ship.
It is another object of this invention to provide tension measuring apparatus that is entirely external to the cable being launched and that requires no electrical connection thereto.
An added advantage of this invention is that the same acoustic signals that encode tension measurements are also usable in determining the location and range of the cables with respect to the laying vessel.